Say the ghosts of Frédéric Chopin, Jean-Baptiste Lully, and Antonio Vivaldi were all spending a weekend in Miami and performing a once-in-a-postlifetime concerto at the Arsht Center to benefit the Greater Miami Youth Symphony. Where would they go to find sheet music and tune their instruments for the night? Probably the place that carries South Florida's largest collection of sheet music — more than 21,000 titles — and employs an in-house luthier. Allegro has been part of Miami's music community for more than 50 years and specializes in string, brass, and percussion instruments. The folks here also teach music to children and adults alike. It's a brick-and-mortar nirvana of all things music. Whether you want a $20 tambourine or a $7,000 — and beyond — violin, the store probably has it in stock. If not, they'll order it — and give you a damn good price in the process.